Coroutines on the way!

This was given on GDG Santiago DevFest 2019

Transcript

1. Coroutines on the way! Armando Picón Android Engineer at Cornershop Inc. @devpicon https://medium.com/@devpicon Using Coroutines in your Android App
2. Long running tasks • Network requests
3. Long running tasks • Network requests • Database operations
4. Long running tasks • Network requests • Database operations • Image processing
5. Long running tasks • Network requests • Database operations • Image processing • ...and more!
6. Challenge 1: Execute on a non-UI thread
7. Challenge 1: Execute on a non-UI thread Challenge 2: Get informed when the task is done
8. Challenge 1: Execute on a non-UI thread Challenge 2: Get informed when the task is done Android solutions • AsyncTask • Loaders (deprecated in Android P) • RxJava • Thread / HandlerThread / Executor with callbacks
9. Threads and callbacks fun login(name, pass) { val thread = Thread(Runnable { requestLogin(name, pass) { result -> show(result) } }) thread.start() }
10. Threads and callbacks fun login(name, pass) { val thread = Thread(Runnable { requestLogin(name, pass) { result -> Handler(Looper.getMainLooper()) { show(result) } } }) thread.start()
11. Threads and callbacks fun login(name, pass) { requestLogin(name, pass) { result -> show(result) } }
12. onDraw onDraw onDraw requestLogin UI Thread fun login(name, pass) { requestLogin(name, pass) { result -> show(result) } }
13. onDraw onDraw onDraw requestLogin UI Thread fun login(name, pass) { requestLogin(name, pass) { result -> show(result) } }
14. onDraw onDraw onDraw requestLogin UI Thread show onDraw fun login(name, pass) { requestLogin(name, pass) { result -> show(result) } }
15. onDraw onDraw onDraw requestLogin UI Thread show onDraw fun login(name, pass) { requestLogin(name, pass) { result -> show(result) } } onDraw onDraw onDraw
16. Coroutine = suspendable computation onDraw onDraw onDraw requestLogin UI Thread show onDraw onDraw onDraw onDraw
17. Coroutine Write asynchronous code sequentially fun login(name, pass) = launch { val result = requestLogin(name, pass) show(result) }
18. Coroutine ~ lightweight thread fun login(name, pass) = launch { val result = requestLogin(name, pass) show(result) }
19. fun login(name, pass) = launch(Dispatchers.IO){ val result = requestLogin(name, pass) withContext(Dispatchers.Main) { show(result) } } Coroutine • Not bound to a specific thread • Complete with a result
20. fun login(name, pass) { requestLogin(name, pass) { result -> show(result) } } requestLogin Thread show Suspension point
21. suspend fun requestLogin( name: String, pass: String ): Result {...}
22. suspend fun requestLogin( name: String, pass: String ): Result {...}
23. suspend fun requestLogin( name: String, pass: String ): Result {...} Las funciones suspendidas no bloquean el hilo de invocación
24. suspend fun requestLogin( name: String, pass: String ): Result = withContext(Dispatchers.IO) { ... }
25. Dispatchers.Main • Main thread • Use it for: UI operations
26. Dispatchers.Default • Common pool of shared background threads • Use it for: computing-intensive coroutines Dispatchers.Main • Main thread • Use it for: UI operations
27. Dispatchers.Default • Common pool of shared background threads • Use it for: computing-intensive coroutines Dispatchers.IO • Shared pool of on-demand created threads • Use it for: IO-intensive blocking operations Dispatchers.Main • Main thread • Use it for: UI operations
28. Dispatchers.Default • Common pool of shared background threads • Use it for: computing-intensive coroutines Dispatchers.Unconfined • Doesn’t confine the coroutine to any specific thread • Don’t use it in code Dispatchers.IO • Shared pool of on-demand created threads • Use it for: IO-intensive blocking operations Dispatchers.Main • Main thread • Use it for: UI operations
29. suspend fun requestLogin( name: String, pass: String ): Result = withContext(Dispatchers.IO) { ... }
30. suspend fun login(name, pass) { val result = requestLogin(name, pass) show(result) } suspend fun requestLogin( name: String, pass: String ): Result = withContext(Dispatchers.IO) { ... }
31. suspend fun login(name, pass) { val authToken = authenticate() val result = requestLogin(authToken, name, pass) show(result) } Sequential
32. suspend fun login(name, pass) { val authToken = authenticate() val result = requestLogin(authToken, name, pass) show(result) } Data dependencies
33. suspend fun login(name, pass) { try { val result = requestLogin(name, pass) show(result) } catch (error: NetworkError){ } } Errors
34. Launching and cancelling coroutines Login button pressed Launch coroutine requestLogin Show login status
35. Login button pressed Launch coroutine requestLogin Show login status val job = Job() val uiScope = CoroutineScope(Dispatchers.Main + job)
36. Login button pressed Launch coroutine requestLogin Show login status val job = Job() val uiScope = CoroutineScope(Dispatchers.Main + job) fun login(username: String, pass: String ) = uiScope.launch { val result = requestLogin(name, pass) show(result) }
37. Login button pressed Launch coroutine requestLogin Show login status val job = Job() val uiScope = CoroutineScope(Dispatchers.Main + job) fun login(username: String, pass: String ) = uiScope.launch(Dispatchers.IO) { val result = requestLogin(name, pass) show(result) }
38. val job = Job() val uiScope = CoroutineScope(Dispatchers.Main + job) fun login( username: String, pass: String ) = uiScope.launch { val result = requestLogin(name, pass) show(result) } job.cancel()
39. Launching and cancelling coroutines Login button pressed Launch coroutine requestLogin Show login status Activity destroyed
40. Launching and cancelling coroutines Login button pressed Launch coroutine requestLogin Show login status ViewModel
41. Login button pressed Launch coroutine requestLogin Show login status ViewModel fun onCleared() { super.onCleared() job.cancel() }
42. class MyViewModel: ViewModel() { val viewModelJob = Job() val uiScope = CoroutineScope(Dispatchers.Main+viewModelJob) fun login( username: String, pass: String ) = uiScope.launch(Dispatchers.IO) { val result = requestLogin(name, pass) show(result) } fun onCleared() { super.onCleared() viewModelJob.cancel() } }
43. class MyViewModel: ViewModel() { val viewModelJob = Job() val uiScope = CoroutineScope(Dispatchers.Main+viewModelJob) fun login( username: String, pass: String ) = uiScope.launch(Dispatchers.IO) { val result = requestLogin(name, pass) show(result) } fun onCleared() { super.onCleared() viewModelJob.cancel() } } lifecycle-viewmodel-ktx
44. class MyViewModel: ViewModel() { fun login( username: String, pass: String ) = viewModelScope.launch(Dispatchers.IO) { val result = requestLogin(name, pass) show(result) } }
45. • Coroutines • suspend functions • Dispatchers • Launching a coroutine • Using a coroutine from ViewModels
46. • Coroutines • suspend functions • Dispatchers • Launching a coroutine • Using a coroutine from ViewModels • Testing coroutines • Using coroutines with other Jetpack libraries • Channels
47. • Kotlin Official Documentation https://kotlinlang.org/docs/reference/coroutines-overview.html • Improve app performance with Kotlin Coroutines https://developer.android.com/kotlin/coroutines • Coroutines in Kotlin 1.3 explained: Suspending functions, contexts, builders and scopes https://antonioleiva.com/kotlin-coroutines/ • Kotlin Coroutines by Tutorials https://store.raywenderlich.com/products/kotlin-coroutines-by-tutorials
48. Ahora es tu turno! codelabs.developers.google.com/ codelabs/ kotlin-coroutines Armando Picón Android Engineer at Cornershop Inc. @devpicon https://medium.com/@devpicon